Multiple scattering in SANS experiments: the different cases and their treatments
Henrich Frielinghaus
Forschungszentrum Jülich GmbH, JCNS at MLZ, 85748 Garching, Germany
In the past years, in my collaborations, we developed the description and the treatment of multiple scattering effects in small-angle neutron scattering experiments. One case considers uncorrelated, multiple scattering events in the sample. This case was already described by Schmatz and Schelten [1]. However, we took also (spin) incoherent scattering into account in order to separate the two signals from each other [2,3]. As a second benefit, the inelastic incoherent scattering could also be included in the description. The latter is highly important for SANS at pulsed sources because the different signals are connected to different wavelengths and, therefore, to different flight times in the instrument. When the scattering probability still increases, the scattering events come closer and closer and finally happen within a single structural unit in the sample [4] (characterized by the correlation length, for instance inside a single colloid). Then, resonances happen to occur at the surfaces of the structures inside the sample. The scattering pattern then is tightly connected to the surface structure instead of the bulk structure. This effect usually appears in USANS and VSANS experiments.
In this talk, the conditions and their meaning is explained in detail. Solutions of the equations are discussed with references to experimental habits. A few selected scientific results are presented to highlight the new achievements.
References
[1] Schelten, J. A., & Schmatz, W. (1980). Multiple-scattering treatment for small-angle scattering problems. J. Applied Crystallography, 13(4), 385-390.
[2] Frielinghaus, H. (2018). Strategies for removing multiple scattering effects revisited. Nucl. Instr. Meth. Phys. Res. A, 904, 9-14.
[3] Jaksch, S., Pipich, V., & Frielinghaus, H. (2021). Multiple scattering and resolution effects in small-angle neutron scattering experiments calculated and corrected by the software package MuScatt. J. Applied Crystallography, 54(6), 1580-1593.
[4] Frielinghaus, H., & Gommes, C. J. (2025). Coherent multiple scattering in small-angle scattering experiments: modeling approximations based on the Born expansion. J. Applied Crystallography, 58(5).